Non mean-field approach to the problem of helix-coil transition in biopolymers will be discussed. The Hamiltonian of the model is constructed using solely the microscopical, pure physical quantities, characterizing the molecular chair, namely the energy of hydrogen-bond formation and the number of conformations of repeated unit. The model is first developed for the polypeptide chains and then the its extension to the DNA molecule is suggested. The advantage of suggested approach is that the parameters of the model are not phenomenological and their actual values are not averaged over the conformational space. Those can be obtained from independent calculations or experiments. The model is generalized to take into account the effect of the solvent on the helix-coil transition. It is shown that the parameters of the traditional Zimm-Bragg theory may be evalated exactly from the microscopical approach.

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